A vital component of research activity at OPR has been and will continue to be access to an excellent population library, known as the Population Research Library (SPR) within the OPR building. SPR is a branch of the University library system. The purpose of the Library Core is to ensure that research staff and faculty associates working on Center-eligible research grants have access to this comprehensive collection of books, articles, and demographic data, and to the high level of service provided by the SPR staff. The Library Core is also in charge of the documentation for all data files in the OPR data archive, including questionnaires, codebooks, and printed tabulations of frequency distributions. Bibliographic services provided by the Library Core include (l) the general dissemination of information by circulating Population Index so that staff can mark items they wish to see and circulating lists of new books added to the collection and lists of locally catalogued materials, (2) targeted dissemination of information by developing individual profiles of interests of each staff member and circulating tables of contents of routed periodicals, (3) bibliographic searches of the OPR catalogue, Princeton University online catalogue, and electronic data bases such as , and (4) documents delivery by acquiring materials from other branches of the Princeton University library system, by borrowing directly from APLIC members, from inter-library services, and by CARL fax-delivery.